Biological Activities of Carrageenans against Human Infectious Diseases

Abstract

Carrageenans are natural sulfated polysaccharides with diverse structures that present a variety of physicochemical properties, which are the basis for their applications in the food, cosmetic and pharmaceutical industries. Carrageenans are normally classified according to their structural characteristics, including their sulfation pattern and/or the possible presence of 3, 6-anhydrogalactopyranose unit on the main structure. Three main forms of carrageenans are commercially used: κ, ι and λ, which differ in their degree of sulfation, solubility and gelling properties. The natural sources of carrageenans are marine algae, mainly red seaweeds, where polysaccharides are present in the extracellular matrix. The polyanionic nature of carrageenans provides them with many biological activities, including antiviral, antitumor, immunomodulatory and anticoagulant effects. In vitro antiviral activity of carrageenans has been demonstrated against several viruses, such as herpes simplex viruses, human immunodeficiency virus, human papillomavirus, flaviviruses (dengue virus), respiratory viruses (human rhinovirus, influenza virus, and human metapneumovirus), and human enterovirus, among others. The antiviral activity of carrageenan is mainly exerted by interference in the viral entry into host cells. The in vivo antiviral efficacy of carrageenans has also been demonstrated in clinical trials, where polysulfates act as microbicides in sexually transmitted infections or are applied as nasal sprays for the treatment of common cold. In this chapter we will focus on the health effects of carrageenans and on the promising potential as therapeutic agents.